1. Field of the Invention
The present invention relates to a receiver which receives an infrared remote control signal, an electronic apparatus having the receiver, and a discharge lamp lighting apparatus having a light-receiving portion which receives an infrared remote control signal.
2. Description of the Related Art
For example, in Jpn. Pat. Appln. KOKOKU Publication No. 6-5638 (pp. 3-4), a plurality of fluorescent lamps are attached to sockets on a chassis. A storage is interposed between the fluorescent lamps on the chassis, and incorporates a light-receiving portion for an infrared remote control signal. An optical filter such as a long-pass filter or band-pass filter is attached to the front end of the light-receiving portion. The filter cuts out most of the argon spectra generated in the initial lighting stage of the fluorescent lamps, and only an infrared remote control signal reaches the light-receiving portion.
The structure with the optical filter attached to a desired function and most of the argon spectra can be cut out when light is incident perpendicularly or almost perpendicularly on the plane of the optical filter. When light is obliquely incident, for example, the peak wavelength shifts toward the short-wavelength direction, failing to obtain a desired function.
FIG. 1A shows the change of a lamp current S1 over time in the initial lighting stage of the fluorescent lamp. FIG. 1B shows the change of a relative argon emission intensity S2. The relative argon emission intensity was obtained by lighting a fluorescent lamp FHC34 (available from TOSHIBA LIGHTING & TECHNOLOGY) at −2° C., and observing an argon emission state upon lighting the lamp by using a photomultiplier tube whose front end was covered with a monochrome optical filter for transmitting an 851-nm ray serving as one of the argon lines.
The waveforms in FIGS. 1A and 1B reveal that variations in the argon spectrum intensity over time synchronize with the lamp lighting cycle. When the lighting frequency is about 50 kHz, the intensity of the argon spectrum in the infrared range also varies at about 50 kHz.
For this reason, if the argon spectrum on a wavelength side lightly shorter than the wavelength of an infrared remote control signal obliquely enters the light-receiving portion via the optical filter and passes through the light-receiving portion, variations in argon spectrum intensity over time may be erroneously determined as a signal from a remote control system, resulting in a malfunction.
The present invention provides a receiver, electronic apparatus, and discharge lamp lighting apparatus which can reduce the influence of variations in argon spectrum intensity over time and reliably extract an infrared remote control signal.